Adapter circuit for establishing connections between automatic and magneto type subscribers



2,516,814 CONNECTIONS BETWEEN AUTOMATIC ANDMAGNETO TYPE SUBSCRIBERS J. H. VOSS ADAPTER CIRCUIT FOR ESTABLISHING 5 Sheets-Sheet 1 m m 1 w 2 5" .w 2 y d m m J F INVENTOR. JOHN H. VOSS ATTORNEY J. H. voss 2,516,814 ADAPTER CIRCUIT FOR ESTABLISHING. CONNECTIONS BETWEEN July 25, 1950 AUTOMATIC AND MAGNETO TYPE SUBSCRIBERS Filed July 2, 1947 FIG. 3

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mmvrok. JOHN H. V055 ATTORMY Patented July 25, 1950 ADAPTER CIRCUIT FOR ESTABLISHING CONNECTIONS BETWEEN AUTOMATIC AND MAGNETO TYPE SUBSCRIBERS John H. Voss, Rochester, N. Y., assignor to Automatic Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application July 2, 1947, Serial No. 758,607

8 Claims. (Cl. 179-84) This invention relates, in general, to telephone systems and, more particularly, to an adapter circuit whereby parties in an automatic ex-' change may ring subscribers on a connecting magneto party line.

The object of this invention is to provide a magneto line adapter circuit of novel and improved design, individual to the magneto line, to thereby allow use of the equipment ordinarily associated with an automatic exchange in completing calls to magneto party lines.

A feature of the invention is the manner in which the sustained code ringing applied to the magneto line is terminated by application of .ringing current to the line by the called subscriber.

Another feature of the invention is the manner in which means in the adapter circuit is operated responsive to an operation by a party on the magneto line to at times establish a connection and at other times to terminate ringing signals to the line.

A, further feature of the invention is the manner in which the called subscriber can terminate ringing current to the magneto line either before or after answering the call.

A further feature of the invention is the manner in which the called subscriber may terminate the application of ringing current to the line only by an operation which is sustained for a predetermined interval of time.

Further features will be apparent from the following specification, having reference to the accompanying drawings comprising Figures 1, 2 and 3 which illustrate a magneto line adapter circuit for use with an automatic exchange, shown connected to a magneto party line, and a manual switchboard.

Referring to the drawings, the system there illustrated comprises a magneto line adapter circuit with line connections 330, 33| and 332 extending to a dial back repeater in an automatic exchange, incoming lines 30!, 302 and 303 which are accessible to a switoh-thru connector or selector in the exchange, line connections I and 2 which extend to a magneto line having a plurality of subscribers, lines 333 and 334 which ex- .tend to ringing interrupter equipment, and tone generating equipment connected to lines 5 and B and tone start lead 339. The magneto line adapter circuit includes a series of relays arranged to operate responsive to seizure over the magneto lines I and 2 or over the lines 30|, 302 and 303 extending from the automatic exchange.

The circuit is efiective to extend a call from the crating circuit to relay 40.

magneto line to the operator at the manual switchboard over lines 330, 331 and 332 when a ringing signal of greater length than a predetermined interval isreceived from a magneto subscriber. The equipment is further effective to extend incoming calls received over conductors 30L 302 and 303 to the magneto lines I and Zand to provide sustained code ringing to sub,- scribers on the magneto line.

Referring now to the operation of the system and-considering firstan incoming call over the magneto lines I and 2 which is to be extended to an operator at a manual switchboard over conductors 330, 33l and 332. The magneto station subscriber applies ringing current to the linein a well known manner for a period of at least 3 seconds,this being a long ring of greater duration than the ordinary long rings used for party line signalling, and a circuit is closed to relay 20 over conductors and 2, contacts H and l3 and the left hand windings of repeater coil 1. Relay 20 operates and at its contact 2| completes an operating circuit to relay over contacts 2| and 43. Relay 50 operates and at its contacts 5| completes an operating circuit to relay 60, at its contacts 52 completes a self-holding circuit over contacts 2| and 52, and at its contacts 53 prepares a circuit for relay 40. Relay operates and at its contacts 6| and-'62 completes an op- Relay 40 operates and at its contacts 42 prepares a point in the shunting circuit of relay 30, at its contacts 43 opens the operating circuit to relay 50, at its contacts 44 completes a circuit to relay 30 over contacts 2|, 43 and 44 and at its contacts 45 prepares a self-holding circuit. Relay 50 is held operated by the self-holding circuit extending over contacts 2| and 52. Relay 30 operates and at its contacts 3| opens the operating circuit to relay 60, at its contacts 32 prepares a further point in the operating circuit of relay I30, at its contacts 33 completes a self-holding circuit'over contacts 2| and 33, and at its contacts 34 completes a multiple holding circuit to relay 40 over contacts GI, 62 and34 and over contacts 6|, 62 and 53. Relay 60 releases and at its contacts 6| opens the multiple holding circuits to relay 40,

and releases its vibrating armature which inter mittently opens and closes an alternate holding circuit to relay 40 over contacts 62 or 63, 45 and 34. Relay 40 holds during the vibrating period contacts 4| completes a circuit to the #1 wind.-

ing of relay I30, at its contacts 43 completes an operating circuit to relay 50, at its contacts 44 opens the operating circuit to relay 30 and at its contacts 45 opens a further point in its selfholding circuit. Relay 50 remains operated. Relay 30 holds over the self-holding circuits aforementioned. The operation of relays 30, 40 and 50 described above requires approximately 3 seconds. If the subscriber transmits a ringing signal of shorter duration than the operating time required by the aforementioned relays, relay 20 will release before the relay chain has fully operated and at its contacts 2| remove ground from the operating circuit for relay 30 which thereupon releases and at its contacts 32 opens a further point in the circuit to relay I30 prior to completion of that operating circuit by release of relay 40 at its contacts 4|. In this manner, party stations on the magneto line maybe assigned code rings consisting of a combination of long and short rings and these parties can signal one another without signaling the operator associated with the line. However, assuming a 3 second ring has been transmitted by the calling subscriber, an operating circuit is completed on release of relay 40 as described heretofore to the operating winding of relay I30 over contacts 32 and 4!.

Relay I30 operates and at its contacts I3I completes a circuit to the tone start equipment, at its contacts I32 connects ground to the common terminal of the top bank of minor switch 210 over line 324, at its contacts I33 prepares a circuit from the CI lead 332 of the dial back repeater to relay 220, at its contacts I34 completes an operating circuit to relay 2B0'over contacts I34, line 328, contacts 2I2, 226,-and 237, at its contacts I35 completes a self-holding circuit over contacts 213, lead 3I3, contacts I83, I35 and I25, at its contacts I36 connects the time lead to the #2 winding of relay I40, at its contacts I31 prepares a circuit for the minor switch rotary magnet 250, at its contacts I38 opens a further point in the impulsing circuit to the minor switch 250, and at its contacts I39 opens a further point in one of the multiple operating circuits for relay 230. Relay 260operates and at its contacts 23! completes an operating circuit to relay 230, which is slow to operate, in multiple: with itself over contacts I34, line 328, contacts 2I2, 228, 231 and 261, at its contacts 262 and 263 prepares part of the loop circuit through the top coil of relay I90 to leads 330 and 33I, and at its contacts 264 completes the circuit from the Cl lead- 332 to fore slow to operate relay 230 is operated, over contacts 264, 236, lead 325, contacts I33, lead .326, and contacts 221. Relay 220 operates and at its contacts 225 which close first completes a self-holding circuit over contacts 2I2 and I34, at its contacts 22 I, 222, 223 and 224transfers the right hand side of the repeating coil to the busy tone lead and ground, at contacts 22I opens its own operating circuit andat contacts 225 opens 4 1 the operating circuits passing over lead 328 to relays 230 and 260. Relay 260 restores and at its contacts 262 and 263 opens the incomplete transmission circuit to the associated dial back repeater, and at its contacts 261 opens the operating circuit to relay 230 before it has a chance to operate. Busy tone isinduced over contacts 222 and line 303 into the left hand winding of the repeater whereby it is returned to the calling party. Relays I30 and 220 remain energized. The calling party, on receipt of the busy tone, applies ringing current to the line for a brief period whereupon relays 20, 50, 60, 40 and 30 reoperate and relay 30 at its contacts 32 closes a shunting circuit to the #1 winding of relay I30. Relay I30 releases and at its contacts I35 opens its self-holding circuit and the holding circuit to relay 200 and restores the adapter circuit to normal condition.

If the central oflice is not busy, relay 220 will not be operated over the CI conductor 332 and relay 230 will be operated after a short interval.

Relay 230 at its contacts 23I and 232 transfers the connector lead to direct ground, at its contacts 233 and 235 completes the loop circuit through the right hand side of the repeating coil I and a circuit for the top winding of relay I90, at its contacts 234 completes the operating circuit to the polarizing winding of relay 90, at its contacts 231 and 238 transfers its own operating circuit and the operating circuit of relay 260 to holding circuits. The polarity of the leads 330 and 33I is such as to prevent operation of relay I90. The dial back repeater is seized by the loop across leads 330 and 33I and the operator is signalled. Relays I30, 230 and 260 are in the energized condition.

When the operator in the central office answers the call, battery on the leads 330 and 33I is reversed and the two windings on relay I30 are polarized in the same direction. Relay I operates and at its contacts I9I completes an operating circuit to relay 2"]. Relay 210 operates and at its contacts 2 completes a self-holding circuit over contacts I34, lead 328, and contacts 2I I, at its contacts 2 I2 opens the holding circuits to relays 230 and 260, at its contacts 2I3 opens the holding circuit to relay I 30, and at its con- .tacts 2I4 prepares an alternate circuit to relays 230 and 200. Relays 230 and 260 are slow to release. Relay I30 releases immediately and at its contacts I3I opens the operating circuit to the tone equipment, at its contacts I36 disconnects the time lead from the lower winding of relay I40, at its contacts 39 completes a holding circuit'over contacts I2, lead 3I3, contacts I33, lead 320, contacts 2I4 to relays 230 and 260 prior to their release. Relays I90, 2I0, 230 and 260 are in the operated condition and voice currents may be transmitted through the magneto adapter circuit from subscriber to operator and vice versa. This circuit supplies no battery for transmission on calls from the magneto line. Voice currents are transmitted by induction through the repeating coil.

In the event that the subscriber on the magneto line failed to ring off when all trunks were busy or abandoned the call before completion, relays I30 and 220' or possibly I30, 220 and 260 would be left in the energized condition. Relay I30 at its contacts I36 completed a circuit from the time lead to the operating winding of relay I40. After a predetermined time, the associated timer closes a ground pulse to the time lead and relay -I40. Relay I40 operatesand at its contacts .pletes an operating circuit to relay I30.

MI and I42 prepares'a self-locking circuit, atits contacts l43-prepares a circuit to relay IIO,- and at its contacts I45 completes an operating circuit to the rotary magnet 250 of the minor switch 210. Therotary magnet of the minor switch operates stepping the wipers 2' and 212 to the first bank contacts and operating the minor switch oil? normal springs 213 and 214. The off normal springs close and prepare the circuits to the release magnet 240 and relay I50. On termination of the ground applied to the time lead, relay I40 releases and atits contacts I45 opens the operating circuit to the rotary magnet250. The rotary magnet 250 releases. A ground pulse is transmitted over the time lead every 30 seconds. Relay I operates each time a pulse is received and effects operation of the rotary magnet causing the minor switch to advance one step. This operation continues until the wiper 2' reaches the contact to which lead 323 is connected, at which time an operating circuit is completed to relay I00 over contacts I32, wiper 21 I, the contact of the minor switch to which lead 323 is connected and contacts I82. Relay I40 and the rotary magnet 250 release as described above when the ground is removed from the time lead. Relay I50 operates and at its contacts IBI inserts a 500 ohm resistor across the connector leads 300 and 3M, at its contacts I62 com- Relay I80 operates and at contacts IBI closes its own locking circuit over contacts I32, lead 324, the top bank of minor switch 210, wiper 2', the previously determined bank contact to which lead 323 is fastened and contacts IBI, at its contacts I02 opens the operating circuit to relay I60, and at its contacts I83 opens the holding circuit to relay I30. Relay I00 restores and at its contacts IE2 opens the operating circuit to relay IBO which holds over the self-holding circuit described above. Relay I30 restores and at its contacts I36 terminates operation of the tone equipment, at its contacts I32 opens the holding, circuit to relay I80, at its contacts I33 opens a further point in the operating circuit for relay 220, at its contacts I30 opens the holding circuit to relay 220, which will be in the operated condition in the event the calling subscriber failed to ring off on receipt of an all trunks busy signal, or relays 230 and 230, which are in the operated condition in the event that the calling subscriber abandoned the call, at its contacts I35 opens a further point in its own holding circuit, at its contacts I33 disconnects the time lead from the lower winding of relay I00, and at its 5 contacts I39 completes an operating circuit to the release magnet 2 30 over contacts I2, lead 3I0, contacts I39, lead 320, contacts 85, lead 322, and the off normal springs 214. The minor switch release magnet 240 operates restoring its .wipers to normal and releasing the oil normal failure to ring oil on receipt of a busy tone, the

second subscriber will receive busy tone when his receiver is lifted. Obviously, the second subscriber can restore the set to normal by ringing ofias described heretofore and then ringing the operator to establish his connection. If the cirqcuit was left in a partially energized condition: as a result of an abandonedcall, the second sub-- scriber will receive ring-back tone and after determining by inquiry as to whether the line is busy or abandoned can ring oil as heretoforedescribed and then apply the long ring to signal the operator. Means are also available to the operator for releasing the circuit before the au-. tomatic release can be effected and willbe more. fully explained at a further point in the disclosure.

Assuming now that the parties have complete their call, relays I90, H0, 230 and 260 operated, the release of the connection is under the control of the operator. The calling party hangs up and applies ringing current'to the line as a ring-down signal. The connection extending over the loop to the operator is opened on .re-- ceipt of the ring-down signal at the adapterxcira cuit in a manner heretofore described and the operator is informed that the call is terminated. If the call has been completed to an automatic subscriber, the operator will release the connection on receipt of the signal extended by the automatic subscriber when his receiver is restored. When the operator disconnects the current through the top winding of relay I90 is reversed. Relay I90 releases and at its contacts ISI opens the circuit to relay 2I0. Relay 2I0 at its contacts 2 I0 opens the operating circuits to relays 230 and 200 which release and restore the circuit to-its normal condition. If the call has been completed to another magneto subscriber, the: connection is released by ring-down signals applied to the line by the subscribers as heretofore described. 2 Assuming now a call is to be completed to a subscriber on the magneto line connected to lines I and 2, the magneto adapter circuit is arranged to be seized through the banks of a standard Strowger type switch-through connector, or selector connected to incoming leads 30I, 302 and 303. When the connector is seized and operated to seize the illustrated adapter circuit, the calling line loop is closed across the leads 302 and 303, and ground is connected to lead -30I. Relay I20 is operated over lead 304, contacts '8I, lead 306, contacts 232- and lead 30I, and at its contacts I2I completes a self-locking circuit to lead 30I, at its contacts I22 and I23 connects Irelay 10 to the incoming lines ;302 and 303 through the right hand winding of repeater coil I, at its contacts I20 opens the circuit-to the upper winding of relay I90 and at its contacts I25 opens a further point in the circuit to relay I30. Relay I0 operates and at its contacts II completes an operating circuit to relay 80 and at its contacts I2 opens a further point in the circuit to the release magnet 240 and relay 230. Relay 80 operates and at its contacts 8| opens the operating circuit to relay I20, at its contacts I2I connects ground to relay I20 over lead 306, contacts 232, lead 30I and contacts I2I and also to the 0 lead 30I of the connector to hold the preceding switch train operated after the preceding switch has removed its temporary ground from lead 30I, at its contacts 83 prepares a circuitlto the upper winding of relay I40 and relay H0, at its contacts 84 prepares a circuit to relay. 90 and. the rotary magnet 250 in multiple, and at its contacts 85 opens a further point in the releasemagnet circuit. The circuit is now prepared .for receipt of the impulses, which represent thelast 'digitof agroup, toselect the code which .isrtobe used in ringing the desired subscriber. Relay 10 operates responsive to the impulses representing the. digit and at its contacts 1| opens and closes the circuit to relay 80 and at its contacts 12 opens and closes the operating circuit to the rotary magnet 250 and to relay 90 over contact 12, lead 3I3, contacts I39, lead 320, contacts 84, lead 32I, contacts I55, I38 and lead 32I. Slow to release relays 80- and 90, operate on the first impulse and remain operated for the duration of the impulses. Relay 30 at its contacts 9| short circuits the lower half of the right hand side of repeating coil 1 to improve impulsing conditions and at its contacts 92 opens a further point in the circuit to the lower winding of relay I50. The rotary magnet 250 follows the impulses and efiects operation of the wipers 2H and 212 one step for each pulse. Incident to the first step oi the switch, off normal springs 213 and 214 are operated and prepare operating circuits for the lower winding of relay I50 and release magnet 240. After the last impulse relay 10 remains in the operated condition and at its contacts 1| maintains an operating circuit for relay 80 and at its contacts 12 opens the circuit to the rotary magnet 256 and relay 90. A short interval later relay 90 releases and at its contacts 9| opens the short circuit to the lower part of the right hand winding of repeater 1 and at its contacts 92 completes an operating circuit to the lower winding of relay I50 over contacts 83, 92, lead3l5, off normal springs 213 and lead 329. Relay I50 operates and at its contacts II closes ground to the R. M. ST lead to start the ringing machine, at its contacts I52 completes a selfholding circuit over contacts 83, lead 3I4, and contacts I52 in multiple with an operating circuit to relay I10, at its contacts I53 connects the PU lead 353 of the ringing interrupter to the upper winding of relay I40, at its contacts I54 prepares a circuit for the A. C. relay It from the selected generator lead of group 215, and at its contacts 155 opens a further point in the operating circuit to rotary magnet 250. Relay I operates and at its contacts I12 and I14 reverses ground and battery over the closed loop comprising the upper and lower winding of relay 10, leads 301 and 309, contacts I12 and I14, contacts I22 and I23, leads 303 and 3H], the right hand windings of repeating coil 1. and the conductors 302 and 303. The ringing interrupter circuit closes a ground pulse to the pickup lead 333 just before the beginning of each code cycle. Relay I40 operates responsive to the ground pulse over lead 333, contacts I53, I42 and H4. and at its contacts NI completes a self-holding circuit over contacts 83, lead 3I4, contacts MI and H4, at its contacts [42 opens the operating circuit from lead 333, at its contacts I43 prepares an operating circuit to relay H0, at its contacts I44 completes the operating circuit to relay I0 from the generator lead selected by the minor switch 210, wiper 212, lead 3I8, contacts I54 and I44, and at its contacts I45 closes a point in the circuit to the rotary magnet 250. The code assigned to the desired subscriber is transmitted by the selected generator lead to relay I0. Relay I0 operates responsive to the ringing current and at its contacts I2 and I4 connects the generator leads 5 and 6 to the magneto lines I and 2 to ring the telephones associated. with this line in accord with the ringing current applied to relay I0. The code is repeated over the line until the subscriber answers by applying ringing current to the line during the interval between code rings or 3 and 4 bridged across the back contacts of relay I0 allow a small amount of ringing current to flow through the left hand windings of repeater coil 1 to return ringback tone to the calling line.

When the called party applies the ringing current for at least 3 seconds to the line in the well known manner to terminate the code ring, relays 20, 50, 60, 40 and 30 operate in the manner heretofore described and an operating circuit is completed to relay H0 over contacts 2i, 33, 3I1, I43 and H2. Relay 20 and the aforementioned relays release on termination of the applied current as heretofore described. Relay H0 operates and at its contacts III completes a self-holding circuit over contacts 83 and III, at its contacts I I2 opens its operating circuit, at its contacts II3 opens the ground connection to the ringing machine, and at its contacts 4' opens the holding circuit to relay I40. Relay I40 releases and at its contacts I4I further opens its self-holding circuit, at its contacts I42 prepares its operating circuit, at its contacts I45 opens a point in the circuit to the rotary magnet 256, and at its contacts I44 opens a point in the circuit to relay I0 to terminate the operation and application of the ringing signal to the magneto line. The circuit is now set up for voice transmission, with relays 1D, 80, H0, I20, I50. and I10 in the operated condition. Transmission battery is supplied to the calling line through the winding of relay 1B and to the called magneto line by a local battery at the station.

When the calling party restores his receiver, i. e., after the call is completed or in the event the called party does not answer, the loop circuit to relay 10 is opened. Relay l0 releases and at its contacts 1I opens the operating circuit to slow to release relay 80, and at its contacts 12 completes an operating circuit to relay 90 over contacts 12, lead 3I9, contacts I33, lead 320 and contacts 85 before relay has suificient time to operate. Relay 90 operates and at its contacts 92 opens the locking circuit to relay I50 which releases and at its contacts I52 opens the holding circuit to relay I10. Relay I10 releases and at its contacts I11, I12, I13 and I14 reverses battery to the line connection. A short interval later, relay 80 releases and at its contacts 82 discon nects ground from the C lead 30I to release relay I20 and the preceding switches and condition the line for subsequent calls, at its contacts 83 opens the holding circuit to relay H0, at its contacts 34 opens the operating circuit to relay 90, and at its contacts 85 completes an operating circuit to release magnet 24'!) over contacts 12, lead 3I3, contacts I39, lead 320, contacts 85, lead 322, and on" normal springs 214. Relay and I20 release. The release magnet 240 operates and restores the minor switch 210 to normal. Off normal springs 214 release and open the operating circuit to the release magnet 240. The circuit is now restored to its normal condition.

The circuit is further provided with verification service whereby an operator may monitor a connection by dialing the special verification number assigned to the line through a standard Strowger type connector which seizes the circuit over lines 340, 34I and 342. Battery connected to the 0 lead 342 through contacts I02 and relay I50 efiect operation of the connector to connect ground to the conductor 342 and thereby complete a operating circuit to. relay I60. Relay It!) operates and at its contacts I6I completes a 500 ohm shunt across the conductors 340 and 3M to operate the ring trip relay inthe connector, which thereupon operates and eifects completion of a transmission circuit through the connector, and at its contacts I62 completes an operating circuit to relay I80. Relay I60 is slow to release and relay I88 is slow to operate to allow sufficient time for the ring trip relay in the connector to operate before the 500 ohm shunt is removed from lines 346 and 34L Relay I8!) operates and at its contacts it! closes a self-holding circuit over the C lead 342 and at its contacts I82 opens the operating circuit to relay I60. Relay It!) operates and removes the 500 ohm. shunt from the lines 3% and 34!, and at its contacts Hi2 opens the operating circuit to relay I88 which holds up over C lead 342 until such time as the operator disconnects to release the connector and consequently relay I88. The operator may listen or talk over leads 340 and 2M with the parties using the circuit.

The verification number may also be used Whenever the calling magneto party fails to ring off after findin all trunks busy as heretofore described. Relays I39 and 221i will be in the perated condition. The circuit will release automatically, but in the event that the operator Wishes to accelerate release of the circuit, she dials the verification number. Relays I64! and I8!) operate as described above and relay I89 at its contacts I83 opens the circuit to relay I30. Relay I30 releases and at its contacts I34 opens the holding circuit to 228. Relay 229 releases. If the minor switch has been stepped off normal, relay 139 at its contacts 535 completes a circuit to release magnet 240 over contacts it, lead 3H9, contacts I39, lead 320, contacts 85, lead 322, and off normal springs 2M1 Release magnet 2 10 operates and effects release of minor switch 215). The off normal springs 214' are opened incident to release of the switch and the operating circuit to the release magnet is opened and the circuit is restored to normal.

While a particular embodiment of the invention has been described, it will be understood that various modifications may be made therein which are within the time, spirit and scope of the invention.

What is claimed is:

1. In a telephone system, a called line comprising a plurality of magneto substations, an automatic exchange including therein a, first means for transmitting impulses, an adapter circuit connected to said automatic exchange and to said called line for extending a, connection from said automatic exchange to said called line, a second means. included within said adapter circult and operated in response to receipt of impulses from said automatic exchange, a third means in said adapter circuit for providing sustained code ringing for selectively signalling a substation of said called line operated in response to the operation of-said second means, a hand generator connected to said called line, and relay means in said adapter circuit operated in response to the ringing current of said hand generator of said called line for terminating said sustained code ringing.

2. In a telephone system, 9, called subscribers line comprising a plurality of magneto substations, an automatic exchange including therein a first means for transmitting impulses, an adapter circuit individually connected to said called subscribers line for extending a connection. to said called subscribers line, an incoming call line connecting said automatic exchange to said adapter circuit, a second means included within said adapter circuit and operated in response to receipt of impulses over said incoming call line from said automatic exchange, a third means for providing sustained code ringing for selectively signalling a substation of said called subscribers line operated in response to the operation of said second means, a hand generator connected to said called subscribers line for applying ringing current to said called subscribers line, and relay means operated in response to the ringing current of said hand generator at said called subscribers line for terminating said sustained code ringing.

3. In a telephone system, a line comprising a plurality of magneto substations, an automatic exchange, an operators position, an adapter circuit connected to said line and including a plurality of paths, one of said paths connecting said line to said operator's position, another of said paths connecting said automatic exchange to said line, means included Within said adapter circuit for providing sustained code ringing for selectively signalling a substation of said line in response to an incoming call over. said other path from said automatic exchange, a ringing generator connected to said line and operated for applying ringing current to said line, relay means operated in response to the ringing current of said ringing generator, means responsive to said relay means in case a call is initiated over said line for said operators position for signalling said operators position over said first path, and other means responsive'to said relay means in case a. call is extended to said line over said other path for terminatingsaid sustained code ringing.

4. In a telephone system, acalled line comprising a plurality of magneto substations, an automatic exchange including therein a first means for transmitting impulses, an adapter circuit connected to said line and to said automatic exchange for extending a connection from said automatic exchange to said called line, a second means included within said adapter circuit and operated in response to receipt of impulses from said automatic exchange, means responsive to the operation of said second means to provide sustained code ringing for selectively signalling a substation of said called line, a hand generator connected to said called line for applying ringing current to said called-line for a predetermined time duration, a'line. relay included within said adapter circuitand operated in response to the ringing current of said hand generator at said called line, means'including a group of relays in said adapter'circuit operated only in response to energization of said line relay for a predetermined .time duration, and a ring-stop relay and circuit operated in response'to the operation of said last means. toprovide for the'termination of said sustained code ringing. I

5. In a telephone system, a line comprising a plurality o magneto substations, each of said magneto substations having a, difierent ringing code assigned thereto, an automatic exchange including therein a first means for transmitting impulses indicative of said ringing codes, an adapter circuit connected to said automatic exchange and said line for extending a, connection from said automatic exchange to said line, a plurality of code ringing conductors each corresponding to a different code, means in said adapter circuit operated in response to the receipt of a series of impulses indicative of one of said ringing codes received from said automatic exchange for selecting one of said ringing conductors corresponding to such ringing code, a ringing relay, a circuit closed after said selection for connecting said selected one ringing conductor to said ringing relay, coded current pulses repeatedly connected to said selected one ringing conductor repeatedly operating said ringing relay over said closed circuit in accordance with said coded current pulses, a source of generator current, means for connecting said source to said line each time said ringing relay is operated to code ring over said line in accordance with said selected code ring conductor, a magneto generator connected to said line for applying ringing current to said line for a predetermined time duration, a line relay included within said adapter circuit and operated in response to the ringing current of said magneto generator, means incl-uding a group of relays operated only in response to the energization of said line relay for a predetermined time duration, and a ring-stop relay and circuit operated in response to the operation of said last means for opening said closed circuit to said ringing relay to stop further operations of said ringing relay for terminating said code ringing.

6. In a telephone system, a line comprising a plurality of magneto substations, an automatic exchange including therein a first means for transmitting impulses, an adapter circuit connected to said line and said automatic exchange for extending a connection from said automatic exchange to said line, a plurality of code generators, a minor switch in said adapted circuit, means for stepping said minor switch to select and connect with a particular code generator in response to the impulses transmitted from said automatic exchange, a ringing relay operated in response to the code current of said selected code generator, a ringing generator connected to said line in response to the operations of said ringing relay to provide repeated code ringing current to said line, a hand generator connected to said line for applying ringing current to said line, a group of relays, means for operating all the relays of said group of relays only in response to the ringing current of said hand generator being applied for a predetermined time duration, and a ringstop relay and circuit operated in response to the operation of said group of relays for terminating said repeated code ringing.

7. In a telephone system, a line comprising a plurality of magneto substations, an automatic exchange including therein a first means for transmitting impulses, an adapter circuit connected to said line and to said automatic exchange for extending a connection from said automatic exchange to said line, a plurality of code genera- 6 tors each corresponding to a different code, a

minor switch, a connect relay in said adapter circuit operated in response to said automatic exchange originating a call over said connection to said adapter circuit, a pulsing relay in said adapter operated in response to the operation of said connect relay, said pulsing relay being responsive to the impulses transmitted by said first means in said automatic exchange for repeating said impulses, means in said adapter circuit for stepping said minor switch to select and connect with one of said code generators in response to said repeated impulses transmitted by said pulsing relay, a ringing relay operated in response to the code current of said selected one code generator, a ringing generator connected to said line in response to the operations of said ringing relay to apply repeated code ringing current to said line, a magneto generator connected to said line for applying ringing current to said line, relay means operated only in response to the ringing current of said magneto generator being applied for a predetermined time duration, and circuit means operated in response to the operation of said relay means for preventing a reoperation of said ringing relay to thereby terminate said repeated code ringing.

8. In a telephone system, a line comprising a plurality of magneto substations, an automatic exchange, an operators position, an adapter circuit connected to said line and including a plurality of paths, one of said paths connecting said line to said operators position, another of said paths connecting said automatic exchange to said line, means included within said adapter circuit for providing sustained code ringing for selectively signalling a substation of said line in response to an incoming call over said other path from said automatic exchange, a magneto connected to said line and operated at one of said substations for applying ringing current to said line for varying durations, the application of said ringing current to said line for short durations being used to selectively signal other substations on said line, relay means in said adapter circuit operated only in response to the ringing current of said ringing generator being applied for a predetermined time duration, means responsive to said relay means in case a call is initiated over said line for said operators position for signalling said operators position over said first path, and other means responsive to said relay means in case a call is extended to said line over said other path for terminating said sustained code ringing.

JOHN H. VOSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 1,127,889 Hinrichsen Feb. 19, 1915 2,100,523 Saunders Nov. 30, 1937 2,137,408 Lill Nov. 22, 1938 

